My expectation is that it would work but somehow defeat the object that the buffer was put there for ... namely to sort of cushion the piston as it reached the end of the cylinder. But I doubt if you would notice any difference. Indeed, one 'tune' is to ditch the buffer washer and set the piston head back a tad by drilling a new pin hole so that you get more swept volume. Again I have never done this myself.
I have made new buffer washers ... the 3/4" tap washer is good, as is rubber sheet and I have also made them from leather.
Cheers, Phil